Effect of Refining and Thermal Processes on Olive O il Properties

Abstract

Olive cultivars Bladi and Arbequina were collected and their oil was extracted (cold press). Oil was refined under bleaching and deodori zation conditions for 30 minutes at 55-50°C and their property was compared with the vir gin olive oil. Virgin and refined oils of the cultivars were processed by fryer heating at 180°C (intervals of 0, 1, 2, 4, and 8 hours) and indexes of fatty acid, free fatty acid, peroxide, thiobarbituric acid, polar compounds, conjugated dienes and trienes, Rancimat, color, total polyphenol, tocopherol, chlorophyll and carotenoid were compared. Results s howed that these oils mainly contained oleic (48.69-60.18%), palmitic (18.31-27. 02%), linoleic (7.54-18.58%), palmitoleic (3.9-3.08%), stearic (1.78-2.53%), and linoleic acids (1.87-0.22%). According to the results, it was recommended to refine virgin olive oil by mild bleaching and deodorization to save bioactive compounds. Due to t he heating condition, the relative amounts of unsaturated fatty acids (22.37-50.6%), p olyphenols, tocopherols, chlorophyll, carotenoid and oxidative stability decreased and th e relative amounts of saturated fatty acids (14.2-17.1%), acidity, peroxide, conjugated d ienes and trienes, polar compounds, and thiobarbituric acid increased significantly, bu t the colorant initially decreased and then increased (P< 0.05). Due to polar compounds, f or frying process, mild refined oil was better than extra virgin oil. Keywords: Bioactive compounds, Bleaching and deodorization, Olive cultivars, Stability indexes, Virgin olive oil.